Variable output pumping apparatus



Sept. 3, 1963 N. D. GRISWOLD VARIABLE OUTPUT PUMPING APPARATUS FiledJune 26, 1962 INVENTOR 0. Gris wold Ive/son 221 4). Q 0W HGENT UnitedStates Patent 3,102,485 VARIABLE OUTPUT PUMPING APPARATUS Nelson 1).Griswold, Lake Jackson, Tex., assignor to The Dow Chemical Company,Midland, MiClL, a corporation of Delaware Filed June 26, 1962, Ser. No.205,360

13 Claims. (Cl. 103-38) This invention relates to pumps and particularlyto reciprocating piston pumps which are capable of deliverin-g varyingvolumes of fluid While the piston or pistons of the pump reciprocate ata substantially constant rate.

Other so-called variable volume pumps have been known for many years forspecific uses, but for one reason or another these pumps are not welladapted for use in mobile service, such as oil and gas Well treatingservice, for example. Such service requires maximum utilization ofavailable horsepower to thereby deliver the maximum volume of pumpedfluid against whatever pressure may develop without exceeding thestrength limits of the equipment. Such requirements necessitates minimumweight and bulk consistent with the achieving of other requirements, andease and reliability in controlling the variable volume feature of thepump while under load. Exceptional reliability is necessary because thepump will be used, at least occasionally, in remote areas wherefacilities are not available for making major repairs and because inwell treating service equipment breakdown can result in great damage tothe well under treatment. For example, a pump breakdown during a wellcementing job could result in the cement setting up in the well casingbefore displacement could be effected between the casing and well borewall.

In conventional well treating pumping units, a power source or primemover, usually an interal combustion engine, transmission (which mayinclude a torque converter) and the pump are disposed on a truck.

Any reduction in weight which can be achieved in the coupling :of powerto the pump of the treating unit would, obviously, permit theconstruction of a lighter treating unit or would permit the constructionof a treating unit having an increased pumping capacity (either involumeor pressure, or both) without exceeding gross weight requirements.

Accordingly, a principal object of this invention is to provide animproved variable volume pumping apparatus which is suitable for use intreating earth wells or the like.

Another object of this invention is to provide an improved variablevolume pumping apparatus which is compact in size with respect to itspumping capacity and power utilization over a wide range of pumpingpressures.

A further object of this invention is to provide an improved mobilefluid pumping system for well treating service or the like.

In accordance with this invention a piston type positive displacementpump achieves an infinitely variable stroke between maximum and minimumlimits through a controlled variable phase relationship between twomechanically interlocked crankshafts. These crankshafts operate throughconnecting rods to an equal-legged walking beam pinned at its centerline'to a plunger crosshead. Similar planetary gear assemblies with the sungears of the assemblies, interconnected by means of a worm and wormwheel, are used to drive the'crankshafts and also to establish andmaintain the desired phase relationship between the crankshafts duringoperation. By rotating the worm and thus changing the phase of theplanetary gears coupled to each crankshaft, the phase relationshipbetween crankshafts and hence the piston stroke may be changed inverselywith the discharge pressure to provide a hydraulic horseice power outputdesirably matched to the available horsepower of the prime mover.

The invention, as well as additional objects and advantages thereof,will best be understood when the following detailed description is readin connection with the accompanying drawing, in which FIG. 1 is asimplified plan view, partly broken away and in section, of apparatus inaccordance with this invention;

FIG. 2 is a sectional view of one of the planetary gear assemblies ofFIG. 1;

FIG. 3 is "a sectional View taken along the line 3-3 of FIG. 1; and

FIG. 4- is a fragmentary end view of drive gears 78a, a showing chaindrive coupling between the drive shafts 36, 38.

Referring to the drawing, there is shown variable volume pumpingapparatus mounted on a common frame (not shown). The apparatus includesa single action reciprocating piston-type pump 12 (see FIG. 3especially) whose piston 14 is coupled to a crosshead plunger 15,adapted to reciprocate in the guide 1511, and to the center of anequal-legged walking beam .16 which in turn is coupled at its ends byconnecting rods 18, 20 to crankshafts 22, 24, respectively, which arejournaled in bearings 17, 19, 21 and 17a, 19a, 21a, for example.

Each of the crankshafts 22, 24 has an end rigidly coupled to a spur gear23, 25 which is rigidly mechanically coupled to another spur gear 29,31, respectively, on a hollow shaft 58, 61), respectively, to which arecoupled the planet gears (46, 48 in FIG. 2) of each of the planetarygear assemblies 30, 32, respectively. The planetary gear assembly 30,shown in section in FIG. 2, is the same as the assembly 32 which isshown in plan in FIG. 1.

The planet gears of each planetary gear assembly 30, 32 are journaled onto shafts 50, 52 (and 54, 56 in FIG. 1) which are fixedly connected bymeans of brackets 59, 61, respectively, to the previously mentionedhollow shafts 58 or 60. Each of the hollow shafts 58, 60 is supported inposition by two bearings 62 and 64 and 62a and 64a, respectively.

Spur gear wheels 78, 80 are rigidly coupled in a fixed rotationalrelationship onto shafts 36, 38, respectively. Each of the shafts isjournaled in bearings 40, 42 and 40a, 42a, respectively, and has one endmechanically coupled to one of the ring gears 26, 28. The gears 78, 80are of equal diameter, have an equal number of teeth, the teeth of onewheel engaging those of the other. Means, such as the spur gear 82 iscoupled to the end of the shaft 36 whereby power from a prime mover 86may be coupled to the shaft 36 through a spur gear 84 and thence throughthe spur wheels 78, 80 to the shaft 38. The power source 86, which maybe an internal combustion engine or a gas turbine, for example, isdiagrammatically indicated by the block 86 and is coupled, as indicatedby a shaft, to the gear 84.

The sun gear (34 in FIG. 2) of each of the planetary gear assemblies 30,32 is rigidly and coaxially coupled to a shaft 65, 67, respectively,which extends through and is coaxial with the hollow shafts 58, 60,previously mentioned. The shafts 65, 67 are journaled in bearings 43, 44and 43a, 44a, respectively.

A worm Wheel 66, 68 is disposed coaxially on and rigidly secured to eachof the shafts 65, 67, respectively, near the end of the shaft which isremote from the sun gear (34 in FIG. 2).

A rotatable shaft 70, Which has worm sections 72, 74 disposed along itslength, is disposed transversely to the shafts 65, 67, the worm sections72, 74 engaging the worm wheels 66, 68, respectively. The shaft 70 isjournaled in bearings such as the bearing 98, for example.

The worm sections 72, 74 have the same pitch and their flights turn inthe same direction of rotation. The worm wheels 66, 68 are of the samediameter.

A hand wheel 76, attached to one end of the shaft 70, is provided forturning the shaft 70 to cause rotation of the worm sections and the wormwheels which are coupled to the sun gears through the shafts 65, 67

Each of the bearings 17, 17a, 19, 19a, 21, 21a, 40, 40a, 62, 62a, 64, 90the pump 12, guide 15a and shaft 70 are mounted on common framework forthe apparatus, which framework also carries the power source '86, theframework being attached to or supported by the mobile unit, e.g., atruck, which carries the apparatus.

In operation the apparatus, as shown, has the hand wheel 76 arbitrarilypositioned so that the angle A is equal to the angle A, for example, inFIG. 3. In this position, the throws of the crankshafts 22, 24 areconnected in an in-phase rotational relationship, and move the piston 14of the pump 12 backwards and forward in the pump cylinder 88 at maximumstroke length as power from the gear 84 is coupled to the shaft 36 and,by means of the spur gears 78, 80, to the shaft 38.

The shafts 36, 38 drive the ring gear (26 in FIG. 2) of each planetarygear assembly 30, 32, respectively. The ring gear of each assembly iscoupled to the sun gear (34 in FIG. 2) of its assembly 30, 32 throughthe planet gears (46, 48 in FIG. 2) of the respective assembly 30 or 32.The planet gears of the assembly are free to rotate on their shortshafts 50, 52 and 54, 56 as the ring gear(s) rotate, but the rotation ofthese pairs of planet gears causes the shafts 58, 60 to rotate, thusrotating crankshafts 22, 24. The sun gears are held in a predeterminedposition with respect to each other by the worm segments 72, 74 on theshaft 70 which do not rotate unless the Wheel 76 is turned. The wormwheels 66, 68, as mentioned previously, each engage with one of the wormsegments 72, 74 and are each coupled in a fixed relationship with one ofthe shafts 65, 67. Because the shafts 65, 67 are mounted in fixedposition except when the wheel 76 is rotated, thus holding the sun gearsin a predetermined position, the rotating of the planet gears (46, 48 inFIG. 2) by the power driven ring gears (26 in FIG. 2) results in therotation of the shafts 58, 60 which are mechanically coupled by gears29, 31 to gears 23, 25, respectively, to the crankshafts 22, 24.

When the stroke length of the piston 14 is to be changed, the shaft 70is turned (as by turning the wheel 76, for example), the amount ofturning depending upon the degree of phase change desired between thecrankshafts 22, 24. As the shaft 70 rotates the worm segments 72, 74rotate and cause the worm Wheels 66, 68 to turn. Such turning is usuallyat a slow rate as compared with the rate of rotation of the crankshafts22, 24. The shafts 65, 67 on which the sun gears (34 in FIG. 2) arerotatably mounted, are rotated as the worm wheels 66 and 68 rotatesupplementing the motion of the sun gears to that of the ring gears toproduce the rotation of the planet gears. The worm segments 72, 74 eachhave the same pitch and their flights turn in the same direction so,with the crankshafts 22, 24 rotating in opposite directions (oneclockwise, one counterclockwise), the relative phasing between theerankshafts 22, 24 is changed as the shafts 65, 67 are rotated. By inphase is meant that the crank throws viewed from the ends of thecrankshafts occupy mirror image positions as in FIG. 3 'where angles Aand A are the same; when angles A and A differ the crankshafts are outof phase. The angular difference between the angles A and A can bevaried by suitably turning wheel 76 and therefore shaft 70, therebyproviding for a variation in the piston stroke length from a maximum toa minimum. The length of the piston stroke is at a maximum when thecrankshafts 22, 24 are in phase as shown. Piston stroke length decreasesas the crankshafts become out of phase 'with respect to each other, thatis, when angles A and A (FIG. 3) differ from each other. When the lengthof the piston stroke is at a minimum one of the connecting rods 18, 20will be at its most forward position with respect to the piston 14 andthe other connecting rod will be at its most rearward position withrespect to the piston. Since both connecting rods 18, 20 are connectedto the walking beam 16 which is coupled at its center to the crosshead15, the movement of the piston 14 is a resultant of the movement of thetwo connecting rods 18, 20 and is practically zero as the walking beampivots around its point of attachment to the crosshead.

When the phase relationship of the crankshafts is at an intermediatepoint between the in-phase relationship and the maximum out-of-phaserelationship there will be some rocking of the Walking beam about itspoint of attachment to the crosshead, and also some forward and backwardmotion of the piston 14.

It should be noted that in the apparatus thus far described, therotation of the drive shafts 36, 38 has been in opposite radialdirection because of the coupling together of the spur gears 78, 80.Thus, even though the rotatable shafts 65, 67 which drive the sun gearsare rotated in the same direction, the phase relationship of thecrankshaft throws is changed.

The same phase relationship of thecrankshaft throws may be achieved ifthe drive shafts 36, 38 are coupled, as by the spur gears 78a, 80a andchain drive 92 shown in FIG. 4, for example, to rotate in the sameradial direction and the worm wheels 66, 68 and worms 72, 74 are adaptedto, on turning the shaft 70, rotate the sun gear drive shafts 65, 67 inopposite radial direction to one another.

The apparatus described above provides means whereby constant horsepowermay be applied to the pump 12 even though the pressure head againstwhich the pump works may vary over a wide range. When the pressure headis low enough to permit such operation, keeping the twocrankshaftsoperating on an in-phase relationship results in maximum volume beingdisplaced through the pump 12. As the pressure head increases the wheel76 is rotated to cause the crankshafts to be moved in an increasinglyout-of-phase relationship with respect to each other so that theavailable driving horsepower may be used to drive the piston 14 inincreasingly shorter strokes and thus deliver less volume at a higherpressure.

Also, since the pump output can be continuously varied betweenpractically no output and maximum output, there is no need for a torqueconverter or an additional speed varying transmission to be interposedbetween the power source and the pump apparatus providing the couplingbetween the power source 86 and the gear 82 does not cause the shafts36, 38 to be rotated at excessive speeds.

While the apparatus has been illustrated as driving a single barrelsingle action reciprocating piston pump, a triplex pump, either singleor double acting, or other multiple cylinder pump may be coupled tosuitable crankshafts which are substituted for the crankshafts 22, 24and which are driven by the planet gear driven shafts 58, 60.

The apparatus of the invention permits the power source to operate at asubstantially constant rpm. rate even through the pumping rate varieswidely. Thus, this apparatus is well adapted to be driven by turbines orby an internal combustion piston-type engine operating at an optimumrpm. rate.

Because the pump is driven by two crankshafts, the bearing loading onthe individual connecting rods is reduced. A single pump may delivereither a large volume at moderate pressure or smaller volume at highpressures. In fixed stroke reciprocating piston-type pumps a socalledhigh volume pump has a relatively low maxmium pumping pressure in orderto prevent overloading of the connecting rod bearings or to prevent thestalling of the prime mover. Conversely, a so-called high pressure fixedstroke piston pump is limited in the volume it can pump at lowerpressures because of the maximum safe rpm. rate of the crankshaft eventhough the connecting rod bearings may not be overloaded and thehorsepower capabilities of the prime mover are not exceeded.

Pumping apparatus in accordance with this invention is more versatilethan conventional apparatus is that it is good both as a highpressure-low volume pump and as a low pressure-high volume pump and itadmits of continuous variation of the relationship between pressure orvolume driving operation. Also, because no intermediate torque converteror speed varying transmission is used, the apparatus is more compact andlighter than a conventional unit of similar work capabilities.

What is claimed is:

l. A mobile pumping unit comprising in combination a prime mover and avariable displacement pump, said pump comprising a cylinder and pistonreciprocal therein, a crosshead, means for mechanically coupling thepiston to the crosshead to reciprocate the piston with reciprocation ofthe crosshead, a walking beam having a central part and two end parts,said walking beam being pivotally coupled at its central part to thecrosshead, a pair of crankshafts, each of said cranlcshafts having atleast one throw, a pair of connecting rods, one of said connecting rodsbeing pivotally coupled to one end part of said walking beam and to athrow on one of said pair of crankshafts, the other connecting rod beingpivotally coupled to the other end of the walking beam and to a throw onother crankshaft, a pair of planetary gear assemblies each comprising asun gear, at least one planet gear and a ring gear, means for couplingone of said crankshafts to said planet gear of one of said planetarygear assemblies, means for coupling the other of said pair ofcrank-shafts to said planet gear of the other of the planetary gearassemblies, a pair of drive shafts, means for coupling said prime moverto said drive shafts and for.

rotating each of said drive shafts, means for operative ly coupling oneof said drive shafts to one of said ring gears, means for operativelycoupling the other of said drive shafts to the other of said ring gears,,a pair of phase control shafts, one of said phase control shafts beingmechanically coupled to the sun gear of one of said planetary gearassemblies, the other of said phase control shafts being mechanicallycoupled to the sun gear of the other planetary gear assembly, a pair ofworm wheels, one of 'said Worm wheels being operatively coupled to oneof the phase control shafts and the other being operatively coupled tothe other of the phase control shafts, and at least one drive wormcoupled to said worm wheels for varying the radial position of the sungear in one planetary assembly with respect to its planet gear and forvarying the radial position of the sun gear in the other planetaryassembly with respect to its planet gear whereby the throw of onecrankshaft has its radial position changed with respect to the radialposition of the corresponding throw of the other crankshaft.

2. A pumping unit in accordance with claim 1, wherein said crankshaftsare disposed parallel to one another.

3. A pumping unit in accordance with claim 1, wherein said drive shaftsare disposed parallel with one another.

4. A pumping unit in accordance with claim 1, wherein the means forcoupling the prime mover to the drive shafts includes means for rotatingthe drive shafts in opposite radial direction to one another and at thesame rate of rotation.

5. A pumping unit in accordance with claim 1, wherein said drive Worm isdisposed along a rod-like shaft.

6. A pumping unit in accordance with claim 5, wherein said means torotate the worm wheels comprises a control wheel which is coupled tosaid rod-like shaft.

'7. A pumping unit in accordance with claim 1, wherein said prime moveris coupled to said drive shaft through fixed-ratio gear means.

8. A pumping unit in accordance with claim 1, wherein said prime moveris a gas turbine.

9. A pumping unit in accordance with claim 1, wherein said prime moveris a reciprocating piston-type internal combustion engine.

, 10. A pumping unit in accordance with claim 1, wherein said at least apart of said means for coupling said crankshafts to said planet gears isa pair of hollow shafts, one of which surrounds each of said phasecontrol shafts.

11. A pumping unit in accordance with claim 1, wherein the sun gear,planet gear and ring gear in one planetary gear assembly are the same asthe corresponding part in the other planetary gear assembly.

12. A pumping unit in accordance with claim 1, wherein the longitudinalaxis of the crank throw of each crankshaft is ofiset from thelongitudinal axis of its crankshaft by an equal amount.

13. A pumping unit in accordance with claim 1, wherein the point ofcoupling of the crosshead to the walking beam is along a lineperpendicular to and bisecting a line drawn between the points ofcoupling of the connecting rods to the walking beam.

References Cited in the file of this patent UNITED STATES PATENTS

1. A MOBILE PUMPING UNIT COMPRISING IN COMBINATION A PRIME MOVER AND AVARIABLE DISPLACEMENT PUMP, SAID PUMP COMPRISING A CYLINDER AND PISTONRECIPROCAL THEREIN, A CROSSHEAD, MEANS FOR MECHANICALLY COUPLING THEPISTON TO THE CROSSHEAD TO RECIPROCATE THE PISTON WITH RECIPROCATION OFTHE CROSSHEAD, A WALKING BEAM HAVING A CENTRAL PART AND TWO END PARTS,SAID WALKING BEAM BEING PIVOTALLY COUPLED AT ITS CENTRAL PART TO THECROSSHEAD, A PAIR OF CRANKSHAFTS, EACH OF SAID CRANKSHAFTS HAVING ATLEAST ONE THROW, A PAIR OF CONNECTING RODS, ONE OF SAID CONNECTING RODSBEING PIVOTALLY COUPLED TO ONE END PART OF SAID WALKING BEAM AND TO ATHROW ON ONE OF SAID PAIR OF CRANKSHAFTS, THE OTHER CONNECTING ROD BEINGPIVOTALLY COUPLED TO THE OTHER END OF THE WALKING BEAM AND TO A THROW ONOTHER CRANKSHAFT, A PAIR OF PLANETARY GEAR ASSEMBLIES EACH COMPRISING ASUN GEAR, AT LEAST ONE PLANET GEAR AND A RING GEAR, MEANS FOR COUPLINGONE OF SAID CRANKSHAFTS TO SAID PLANET GEAR OF ONE OF SAID PLANETARYGEAR ASSEMBLIES, MEANS FOR COUPLING THE OTHER OF SAID PAIR OFCRANKSHAFTS TO SAID PLANET GEAR OF THE OTHER OF THE PLANETARY GEARASSEMBLIES, A PAIR OF DRIVE SHAFTS, MEANS FOR COUPLING SAID PRIME MOVERTO SAID DRIVE SHAFTS AND FOR ROTATING EACH OF SAID DRIVE SHAFTS, MEANSFOR OPERATIVELY